1. Field of the Invention
The present invention relates broadly to surgical instruments for use in the dissection of tissue. More specifically, the present invention relates to surgical instruments for rotating dissecting tools and footed attachments therefor for the purpose of protecting sensitive tissue from exposure to the cutting action of the dissecting tool while cutting bone.
2. Summary of the Prior Art
Surgical instruments for rotating dissection tools to dissect bone long have been employed in the medical arts. Such surgical instruments have particularly utility when used as craniotomes. Craniotomes are surgical instruments employed in the surgical procedure known as craniotomy. Craniotomy involves opening the skull so that access thereto may be had to perform neurosurgery or the like. Typically, craniotomy is performed to remove a section of skull by drilling a series of holes through the cranial bones at points defining the perimeter of the cranial section to be removed. Next, the series of holes are connected by a craniotome in a procedure not unlike the use of a conventional jigsaw.
A danger present in such craniotomies is the risk of penetrating too far into the skull, piercing the dura (the membrane protecting the brain) and into the brain itself. Obviously, if the dura, and the brain underlying it, are penetrated, very serious damage can occur. Consequently, surgical instruments for use in craniotomies are provided with footed attachments or duraguards for protecting the dura and underlying brain from the cutting action of the dissecting tool. Duraguards and similar attachments are shown in U.S. Pat. No. 2,429,356, Oct. 21, 1947, to Hicks; U.S. Pat. No. 3,223,088, Dec. 14, 1965, to Barber et al.; U.S. Pat. No. 3,308,828, Mar. 14, 1967, to Pippin; and U.S. Pat. No. 3,340,060, Jul. 20, 1982 to Berke et al.
One drawback to most prior-art duraguards or footed attachments is that they are fixed relative to the surgical instrument itself. Typically, it is necessary to turn the direction of cutting of the surgical instrument to complete the dissection of a segment of the cranium. This turning necessitates rotation of the entire surgical instrument, which cannot be accomplished easily in the relatively narrow kerf formed by the dissecting tool. Thus, a plurality of pilot holes initially must be bored in the skull to accommodate the turning of the surgical instrument. Prior-art U.S. Pat. No. 4,071,030, Jan. 31, 1978, to Hedrick, discloses a duraguard that is freely rotatable, on ball bearings, relative to the remainder of the surgical instrument. However, because the duraguard is freely rotatable, such a prior-art duraguard is susceptible to undesirable rotation and migration from behind the dissecting tool. If such undesirable rotation or migration occurs, the ability of the user to guide the surgical instrument may be impaired, and the possibility of mistakes increased.
A need exists for a footed attachment or duraguard for use with a surgical instrument for rotating a dissecting tool, wherein the footed attachment is provided with indexing means to permit selective rotation of the footed member or duraguard from one angular position to another, and wherein the indexing means is further provided with a means to secure the footed member or duraguard in any number of selected angular positions relative to the surgical instrument.